This invention relates to deployment of radio systems and more particularly to systems and methods providing for the placement of transmitter/receiver paths to provide links at desired locations while minimizing interference.
In the past, high frequency high bandwidth wireless communication has been provided through the use of point-to-point radio systems, such as point-to-point microwave radio transmitters and receivers providing line of sight communications. Portions of the microwave spectrum of frequencies are made available for use in such point-to-point systems. High frequencies, such as the above mentioned microwave spectrum of frequencies, are generally desirable in providing high bandwidth communication because of their ability to provide large bandwidth in a relatively narrow portion, or channel, of the spectrum.
Presently, one desiring to establish point-to-point communications references a record of all the sites currently established using such microwave communications, and determines where a new link may be established which does not interfere with or receive interference from these established links. This has generally been acceptable where link deployment is scattered. However, the above described technique for deployment is not well suited for mass deployment of such radio links, such as is useful in the metropolitan area wireless networks shown and described in the above referenced patent application entitled COMMERCIAL NETWORK TOPOLOGIES UTILIZING POINT TO POINT RADIOS. Accordingly, other solutions must be utilized for mass deployment of radio systems. One such solution is shown and described in the above referenced patent application entitled SYSTEM AND METHOD FOR ESTABLISHING A POINT TO POINT RADIO SYSTEM. This solution allows for the mass deployment of radio systems through the regulated positioning and orientation of the communication nodes.
Before wireless high frequency communication service can be provided on a mass basis in an area there should exist a deployment technique that can support the planned service in order to provide for the desired location of links without restricting the ability to locate other links where necessary or desired. In order to provide for a dense deployment pattern, such a technique should be able to deploy a large number of radio links established where the antenna gain is at its maximum, i.e., two way radio communication established through main beams of both transmitting and receiving antennas, in a given area such that the individual radio links do not significantly interfere with one another.
There are a number of parameters that determine the magnitude of such interference, such as the antenna gain in the path of the interference, the xe2x80x9chopxe2x80x9d distance between interfering and interfered systems, polarization isolation and frequency channel separation. For example, interference is at its worst when the interfering transmitting main beam is directed towards the interfered receiving main beam, somewhat less when the interfering main beam is directed toward the interfered receiving sidelobe, and even less when the interfering transmitting sidelobe is directed toward the interfered receiving sidelobe. Additionally, the interference decreases the farther apart, i.e., the greater the xe2x80x9chopxe2x80x9d distance between the interfering and the interfered.
A good example of a radio frequency deployment scheme is the cell structure currently in use for cellular wireless service, which may be utilized in fixed location point-to-multipoint systems, which utilizes frequency reuse techniques. The cellular structure provides a model to show that the interference is controllable by frequency reuse and sectorization. Typically, in a cellular network, each set of frequencies is reused in every seventh cell, with each cell divided into three sectors, thereby defining a cellular frequency reuse pattern.
Cellular networks are broadcast based such that a transmitter sends out signals into a designated area and any properly tuned receiver within that area can pick up the signals. However, where radios work at high frequencies, such as point-to-point microwave systems typically operating above 18 GHz, the wavelengths are short so that for effective communication the transmitter and receiver are preferably pointing essentially directly at each other, i.e., line of sight. Such narrow beam transmission implies that the transmitters and receivers are all in fixed positions with respect to each other where their density is not great. Thus, in contrast to cellular systems, there is generally no need in these high frequency systems to xe2x80x9cblanketxe2x80x9d a given area with transmitted signals. This line of sight characteristic has allowed prior point-to-point systems to be constructed without much regard to each other.
However, interference between discrete systems will result when a particular receiver is within the radiation pattern of more than one transmitter. Accordingly, as the demand for high bandwidth communication systems increases the ability to establish links, deployed according to the above described technique, experiencing interference at or below desired levels becomes increasingly difficult. For example, existing links may be positioned and oriented such that an additional link from a particular location, such as an additional office building to be provided service, may not be able to be established due to unavoidable interference from existing links deployed without regard to any other links. Such a technique is not conducive to the implementation of densely deployed radios.
Further, as the number of desired nodes and network complexity increases, the complexity of the interference between nodes expands exponentially. Existing planning tools are unable to effectively and in a timely manner handle interference computations for such large sets of possible node combinations and permutations.
Thus, a need exists in the art for a system and method for developing a radio frequency deployment plan for transmitter/receiver pairs so as to minimize interference while providing for establishing links at desired sites. This system and method should identify the radio frequency plan efficiently. Further a need exists for the location of the desired sites to be freely located within a service region.
A further need exists for such a system and method in which not all of the communication links need be deployed at any time, but which will accommodate growth in any direction throughout the deployment region.
A further need exists for a system and method in which multiple combinations and permutations forming a network of sites are considered, analyzed and an optimized topology is identified.
A further need exists for such a system and method to consider environmental factors in its development of the radio frequency plan.
These and other objects, features and technical advantages are achieved by a system and method which provide a technique by which radio links may be densely deployed with minimized interference by making link determinations based on analysis of acceptable link combinations. According to a preferred embodiment of the present invention, multiple levels of link analysis are performed to determine an optimum network link configuration.
Preferably, the set of possible links connecting the various nodes of an RF network are first analyzed to identify the subset of practicably realizable links, i.e., those links which are within effective range, within line of sight and having an acceptable path loss in view of system gains. Interference analysis is then performed between sets of links so as to identify mutually independent and mutually exclusive links, i.e., links that do not exclude other links and those that impede the inclusion of other links. Mutually exclusive links are eliminated from the feasible set which is then subject to further selection and optimization to arrive at a preferred network topology.
Alternately, a first high order link analysis is performed, such as by a master radio frequency (RF) planning tool, which analyzes all links possible between an identified group of network node sites (transmitter/receiver sites) to determine a potentially usable subset of all possible links. This subset of all possible links identifies links suitable for establishing communication between all identified network node sites. This subset of links is optimized by excluding links not meeting a first order criteria and includes links which do meet first order criteria.
In this embodiment, the first order criteria is established according to a simple set of design rules adapted to allow the master RF planning tool to analyze a large number of mutually interfered radio links, i.e., all links possible between an identified group of network node sites, without requiring excessive processing resources and/or excessively long analysis times. Such design rules may be derived by reducing the number of parameters considered in this first order analysis, such as by analyzing the links in only two dimensions and/or by establishing particular design threshold parameters and simplified link modeling data. Accordingly, a manageable number of rules for the possible link situations may be identified and applied to a very large number of possible links to include and/or exclude links from the potentially usable subset of links.
The subset of links determined by the master RF planning tool may be further optimized by selection of the most preferred links of alternative link paths determined suitable for establishing communication between all identified network node sites which meet the first order criteria. Accordingly, parameters such as link distance, number of link hops between particular nodes, average number of link hops between subscriber nodes and service provider point of presence nodes, and the like may be used in selecting particular links of the subset of links where multiple ones of all of the possible links are determined to meet the first order criteria.
After a first order analysis of the possible links has been concluded, providing a potentially usable subset of links, a second order link analysis is performed, such as by a radio link design tool, which analyzes links of the first order subset of links according to a more detailed analysis than that of the master RF planning tool in order to more accurately determine the suitability of each of these potentially usable links for communication services. Specifically, the radio link design tool takes into consideration link parameters which were not considered in the first order analysis. For example, where the master RF planning tool analyzes links only in two dimensions, such as by implementing the aforementioned preferred embodiment set of design rules, the radio link design tool may provide a three dimensional analysis of the links of the subset of links. Likewise, this second order analysis may utilize more sophisticated and more complicated link modeling data to more accurately analyze links of the subset of links for their suitability in providing the desired quality of communication. In this embodiment, the radio link design tool analyzes links of the subset of links to determine if propagation in free space is likely to provide desired communication signal quality or if such propagation is impeded, such as by a building or other terrain feature of the deployment region blocking the line of sight, causing intolerable multipath conditions, or the like. Accordingly, the radio link design tool may determine that particular ones of the links of the subset of links are unsuitable for use in providing communication at a desired quality level.
If the radio link design tool determines ones of the links of the subset of links are unsuitable for use in providing communication at a desired quality level, the present invention preferably removes this, or these, particular links from the group of all possible links in the master RF planning tool. Thereafter, first order analysis may again be performed which analyzes all remaining links between the identified group of network node sites to determine another potentially usable subset of all possible links. This subset is then preferably analyzed according to the second order analysis as described above. In this embodiment, this sequence of first and second order analysis is performed until the subset of links is found to include links suitable for use in providing the desired communication quality.
After the second order analysis has determined that links of the subset may be utilized to provide the desired communication quality, a communication network system is deployed, altered, or expanded to provide links according to the results of the first and second order analysis described above. Communication is preferably established over these deployed links, such as initially in a commissioning phase, to provide a third order analysis in the form of empirical field verification. Such field verification may include the operation of communication equipment of the links of the network system to provide worst case operation scenarios to confirm communication signal quality levels provided under such conditions. Additionally or alternatively, field verification may include analyzing communication parameters at various ones of the links during communication of signals at other links of the network in order to determine the actual mutual interference experienced.
The field verification information derived from such analysis is used in updating the master RF planning tool and/or the radio link design tool of the present invention. For example, if particular links are discovered to provide communication quality less than that desired, these particular links may be removed from the possible links in the master RF planning tool. Similarly, data relevant to accurately modeling the links of the network, such as link degradation due to topological anomalies or mutual interference caused by multipath conditions, may be provided to the radio link design tool for more accurate determination of links useful in providing the desired communication quality.
In this embodiment, a fourth order analysis is provided in the way of in-service analysis of the links. It shall be appreciated that although referred to herein as fourth order analysis, the in-service analysis may be provided in lieu of third order field verification as well as in addition to field verification. The in-service analysis of the links monitors link parameters during normal use of the links. Such parameters may include link quality measurements, such as a bit error rate, carrier to interference ratio, signal to noise ratio, link outage times, and/or the like, as well as operating parameters of interest, such as receive signal strength, transmission power level, traffic loading, and/or the like.
This in-service information is used in updating the master RF planning tool and/or the radio link design tool of the present invention. For example, link quality measurements may be utilized in providing the above mentioned optimization of the links selected as the subset of links by the master RF planning tool. Additionally or alternatively, in-service information may be utilized by the radio link design tool to more accurately model the links of the networks.
An embodiment of the present invention provides for the ability to build out the communication network, i.e., expand an initially deployed communication network by adding additional links to newly served nodes, by not only considering currently desired links, but also by considering future links. According to this embodiment, the identified group of network node sites analyzed according to the present invention includes at least two categories for grouping of network node sites; installed node sites and future node sites. By including not only the installed node sites in the link analysis but also the future node sites, the links which are currently established may be adapted to easily accept the addition of links of the future node sites as demand increases.
Another embodiment of the present invention further breaks down the future node site category described above to include an upcoming node site category and a potential node site category, to thereby include at least three categories for grouping of network node sites. Accordingly, this embodiment of the present invention provides a hierarchy of future node sites to both allow for consideration of all potential future node sites in the link analysis of the present invention as well as to allow for efficient detailed analysis of a reduced number of links associated with higher precedence links as identified by the further node site hierarchy.
Utilizing a hierarchy of links, such as provided by the future node site hierarchy of the embodiment described above, an embodiment of the radio link design tool does not perform the second order analysis on all links of the subset of links provided by the first order analysis. Instead, the radio link design tool provides its detailed level of analysis only on those links of the subset of links which are most likely to actually be placed into service. For example, where the node sites are categorized as installed node sites, upcoming node sites, and potential node sites, the radio link design tool may perform detailed analysis only on those links associated with installed node sites and upcoming node sites, i.e., those nodes actually installed and those nodes scheduled for service in the future. Accordingly, potential node sites, i.e., those sites suitable for providing network communication thereto and/or those sites meeting some minimum threshold criteria such as a business location currently utilizing an identified minimum communication resource, may be omitted from this more resource demanding level of analysis.
Although the more detailed level of analysis is omitted with respect to particular ones of the links in this embodiment, it should be appreciated that these links have not been entirely omitted from the analysis according to the present invention. Specifically, the embodiment with the master RF planning tool of the present invention provides an analysis on every link possible for all identified node sites, whether they be installed, upcoming, or potential. Analysis of every possible link of this potentially large number of node sites is economically provided according to this embodiment in part due to the set of design rules utilized by the master RF planning tool embodiment, which will provide a good indication of links associated with the potential node sites which will not provide the desired communication quality level.
Another embodiment of the present invention identifies a distributing node site of the node sites to handle a large number of radio links. Analysis according to the present invention may be utilized to determine a maximum number of links possible from such a distributing node site in order to provide for the efficient communication between a large number of radio links and this distributing node site. Such an arrangement is especially useful in situations where communication services are being provided by a service provider, such as a competitive local exchange company (CLEC) or Internet service provider (ISP), through a single switch center or point of presence (POP) which may be coupled to the communication network through the distributing node site.
Additionally, a plurality of such distributing nodes may be utilized to provide back hauling or concentration of communications between a central point, such as the above mentioned switch center or POP, and a large number of nodes of the network and/or nodes of the network which are distributed over a large geographic area. For example, geographic regions may be established wherein the node sites of each geographic region are coupled to a distributing node associated with that particular geographic region for communication with a switch center or POP serving the geographic regions.
Another embodiment of the present invention is a methodology of designing an automated RF planning tool which includes incorporating criteria, such as RF characteristics and potential interference, to determine the desirability of wireless links between possible radio nodes. This methodology also includes the elimination of potential wireless links between radio nodes based on these criteria and the determination of a preferred topology by examining the reduced number of wireless links to be considered. The potential links may be classified as mutually independent or mutually exclusive based on those interference considerations and environmental factors may be included in the determination of the preferred topology.
Accordingly, it is a technical advantage of the present invention that links of a network communication system are analyzed to provide a deployment of links adapted to readily accept future expansion of the network. A further technical advantage of the present invention is realized by the analysis of radio links of the network system include not only installed links and planned upcoming links, but also all potential links between network node sites meeting particular criteria.
It is a still further technical advantage of the present invention that utilization of resources in providing the analysis of communication links is economized through the use of hierarchies of node sites or links in order to allow analysis of all potential links without necessitating excessive resources in providing detailed analysis of such links.
By utilizing a simplified set of link design rules, analysis on a very large number of links, such as the an embodiment which performs an analysis of all possible links between the identified node sites, is possible economically, thus providing a yet further technical advantage.
A further technical advantage of the present invention is provided through the use of multiple orders of analysis of links to efficiently utilize resources as well as to confidently provide communication network link planning to meet desired communication quality levels. Moreover, a technical advantage is provided in that optimization of links is provided through interaction of ones of the multiple orders of link analysis.
A still further technical advantage is realized by the use of the present invention to provide a large or maximum number of links from a particular node site, such as may be designated a distributing site, in order to couple a large number of network node sites to a particular service. This technical advantage may be further compounded by the use of multiple ones of these distributing sites to couple larger numbers of node sites and/or geographically disbursed node sites to such a service.
A still further technical advantage of the present invention is the use of geometric relationships between the radio node sites to eliminate links from further consideration. This advantage is obtained through a multi-step process in which all possible links are identified, these links are classified by their geometric relationship, interfering links are eliminated, topologies are identified which allow communications between all radio sites and a favored topology is selected.
A still further technical advantage of the present invention involves the simplification of complexed interference calculations to enable simplified derivatives of acceptable results through table look ups.
A further technical advantage is to provide the planner the ability to include environmental propagation considerations involving rain and storms in their planning.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.